Acrylic rubber-urethane-acrylate paint and painting process

ABSTRACT

A radiation-curable paint binder dispersion comprises the addition product of a hydroxy-functional acrylic rubber particle, a diisocyanate and a hydroxyalkyl acrylate and vinyl monomers. The dispersion is applied to a substrate as a paint film and cured thereon by exposure to an electron beam.

D United States Patent [151 3,660,143 Johnson et al. 1 May 2, 1972 [54]ACRYLIC RUBBER-URETHANE- [56] References Cited ACRYLATE PAINT ANDPAINTING UNITED STATES PATENTS 3,423,48! H1969 Milulzmi 260M136 I II]Invrnlms: ()Iln ll. Johnson. Livunizl; Sulllnkh 8. 1431514 4H9) f'f'i-26U/872 Lulmml. Dearlmrn llcighls, lmlh of Mich. 35150-796 (/1969WZGO/ms 3.502,?45 3/1970 Minion 260/88! [73] Assigncc. Ford MotorCompany. Deurborn. Mich. 3 509 234 4/1970 HUI-[am u HMO/859 [22] Filed:Dec 21 1970 3,528,844 9/1970 Burlant ..260/885 [211 App]. No 100,477Primary ExaminerPaul Lieberman Att0rneyJ. R. Faulkner and O. B. Johnson52 us. Cl. ..117/93.31, 260/77.5 CR, 260/77.5 TB, 7 ABSTRACT 260/80.75,260/859 51 Int. Cl. ..C08g 41/04, COSg 22/00 A radifliion-curable Paintbmder dispersion comprises the [58] Field of Search ..260/77.5 CR, 859,885; Product of a hydmxy-functiwal acrylic rubber Particle, 117/9331 adiisocyanate and a hydroxyalkyl acrylate and vinyl monomers. Thedispersion is applied to a substrate as a paint film and cured thereonby exposure to an electron beam.

12 Claims, No Drawings l. PREPARATION OF THE ACRYLIC RUBBER PARTICLE Theacrylic rubber particle is a crosslinked, elastomeric, acrylic polymerhaving hydroxy functionality.

These particles can be prepared in either an aqueous or organic medium.

In one method of preparation, a major amount of monoacrylate is emulsioncopolymerized with a crosslinking amount of a dior trifunctional monomercontaining two or more non-conjugated terminal ethylenic groups,preferably a diacrylate, using a water-soluble free radical initiatorand a suitable surfactant to yield a latex of relatively uniformparticle size, e.g., 0.04 to 1 micron averagediameter.

The monoacrylate component of the monomer mixture comprises about 80 toabout 98 mole percent of the mixture while the balance, the diortrifunctional component, constitutes about 2 to about 20 mole percent.The monoacrylate component contains about 65 to about 98, preferablyabout 70 to about 95, mole percent of a monofunctional, alkylmonoacrylate and about 2 to about 35, preferably about 5 to about 30,mole percent of a hydroxyalkyl acrylate. The monofunctional, alkylacrylate is preferably an ester of a C C, monohydric alcohol and acrylicacid, e.g., ethyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate and/or mixturesof the same. Certain other alkyl acrylatesmay be used'when a crosslinked polymer thereof has an appropriate 7glass transition temperature, e.g., dodecyl acrylate. Butyl acrylate and2-ethyl hexyl acrylate are the most preferred of the monofunctional,monoacrylates for use in forming this rubber. The hydroxyalkyl acrylateis preferably the ester of either acrylic or methacrylic acid and a C Cdiol, e.g., hydroxyethyl acrylate, hydroxyethyl methacrylate,hydroxypropyl acrylate, hydroxypropyl methacrylate, or mixtures of thesame. The glass transition temperature of the crosslinked polymer shouldbe such that the particle retains its rubber-like properties attemperatures to which the paint would normally be exposed.

Suitable crosslinking agents include, but not by way of limitation, 1,3butylene diacrylate, 1,3 butylene dimethacrylate, divinyl benzene, 1,6hexamethylene diacrylate, 1,6 hexamethylene dimethacrylate, 1,1,1trimethylolethane triacrylate, 1,1,1 trimethylolethane trimethacrylate,1,1,1 trimethylolpropane triacrylate, 1,1,1 trimethylolpropanetrimethacrylate, 1,4 dimethylolcyclohexane dimethacrylate, allylacrylate, allyl methacrylate, methallyl acrylate, methallylmethacrylate, diallyl maleate, diallyl fumarate and diallyl phthalate.In one embodiment, the crosslinking agent is a diester of acrylic ormethacrylic acid and a C C preferably a C C dihydric alcohol. in anotherem- I bodiment, the crosslinking agent is a triester cf acrylic ormethacrylic acid and a C C preferably a C C trihydric alcohol.

The polymerization process is continued to yield a stable latex ofrelatively uniform particle size and composition. The latex iscoagulated, washed, and dried to yield finely divided powder suitablefor use in this invention.

The monomer charge is emulsified by one or more micelleforming compoundscomposed of a hydrophobic part, such as a hydrocarbon group containingeight or more carbon atoms, and a hydrophilic part, such as alkalinemetal or ammonium hydroxide groups, phosphate or sulfate partial estergroups, sulfonate groups, and the like. Exemplary emulsifying agents umstearate; sodium oleate, the sodium alkyl aryl sulfonates;polyoxymethylene sulfates and phosphates; the ethylene oxide condensateswith long chain fatty acids, alcohols, and mercaptans and the alkalimetal salts of rosin acids. These materials and the techniques of theiremployment in emulsion formation and maintenance are well known to theart and have no unusual application here. As they are conventionalmaterials employed in a conventional manner, further description andexplanation is unnecessary.

A polymerization initiator is composed of one or more water-soluble,free-radical-generating species such as hydrogen peroxide or sodium,potassium, or ammonium persulfates, perborates, peracetates,percarbonates and the like.

As is well known in the art, these initiators may be associated withactivating systems such as redox systems which may incorporate mildreducing agents such as sulfites and thiosulfites and redox reactionpromoters such as transition metal ions.

A chain transfer agent or a mixture of chain transfer agents may beadded to the reaction medium to limit the molecular weight of thecrosslinked acrylic polymers. Such chain transfer agents are generallymercaptans such as dodecanethiol, benzenethiol, pentanethiol andbutanethiol. Those skilled in the art will be aware that otheremulsifying agents, polymerization initiators and chain transfer agentsmay be used when compatible with the polymerization systemhereinemployed. The reaction may be carried out at temperatures fromabout 40 C. to about C., or at lower temperatures, as from 0 C. to 80 C.in the case of activated systems.

In another method of preparation, hereinafter illustrated, the rubberparticles are formed in an aliphatic hydrocarbon medium.

II. THE DIISOCYANATE REACTAN T The preferred diisocyanate for use inthis invention is toluene diisocyanate and this may be either the 2,4-or 2,6- isomer or a mixture thereof. This diisocyanate maybe usedwithout blocking or one of the isocyanate groups thereof may be blockedwith caprolactam or other suitable blocking agent before use. One mayalso use other diisocyanates so long as one of the isocyanate groups isblocked with caprolactamor other suitable blocking agents.Representative of other diisocyanates which can be monoblocked are thefollowing:' 4,4 diphenylmethane diisocyanate, 1-phenoxy-2,4 phenylenediisocyanate, l-tert-butyl- 2, 4 phenylene diisocyanate, and l-ethyl 2,4phenylene diisocyanate. Such blocking allows for separate stagereactions of the two isocyanate groups. Other blocking agents such asphenols and tertiary butyl alcohols may also be used. The blockingagents are selected so that the blocked isocyanate group is converted tofree isocyanate group at a temperature range of about to about C.Sometimes a catalyst such as triethylene diamine or stannous octoate maybe advantageously used in 0.05 to 1 percent concentration (basis weightof reactants) to assist the deblocking process. A diisocyanate can bemonoblocked with caprolactam by reacting the diisocyanate withcaprolactam in toluene. When the first isocyanate group is blocked, themonoblocked product precipitates out of solution. See Raymond R. Myersand J. S. Long, Film-Forming Compositions, Vol. 1, Part 1, page 485,published by Marcel Dekker Inc., New York, N. Y., U.S.A. 1961 The reasonfor using the monoblocked diisocyanates is to assure that only one ofthe isocyanate groups per diisocyanate molecule will react with thehydroxy functionality of the include alkali metal sulfonates of styrene,naphthalene, decyl rubber particle. The second isocyanate group of themolecule is thus left to react with the hydroxyalkyl acrylate therebyproviding the addition product with alpha-beta olefinic unsaturation.When an excess of diisocyanate is employed and not removed prior tointroduction of the hydroxyalkyl acrylate, there will be formedcorresponding amounts of the addition product of one mole diisocyanateand 2 moles hydroxyalkyl acrylate. This provides no problem since thismaterial is copolymerizable with the other paint binder components,increases the concentration of urethane linkages in the resultant paintfilm, and serves as a viscosity modifier.

III. THE HYDROXYALKYL ACRYLATE A hydroxyalkyl acrylate is reacted withthe second diisocyanate group in the next step of the process. Thiscomponent is preferably employed in slight excess of the amount requiredto react with the remaining isocyanate groups. The preferredhydroxyalkyl acrylates are hydroxyethyl acrylate, hydroxyethylmethacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, andmixtures of the same.

lV. VINYL MONOMERS EMPLOYED IN THE PAINT DISPERSION The paint dispersionadvantageously contains about 20 to about 90, preferably about 30 toabout 65, weight percent vinyl monomers and about to about 80,preferably about 35 to about 70,.weight percent of therubber-urethane-acrylate addition product. Monomer type andconcentration provide one means for adjusting the viscosity of the paintsolution to conform to the method of application desired, e.g., spraycoating, roll coating, etc. In functional terms, the amount of vinylmonomer present is at least sufficient to convert the alpha-beta,olefinically unsaturated, rubber-urethane-acrylate addition product intoa crosslinked continuous coating on the surfaces of a substrate when afilm of such coating solution is exposed to ionizing radiation, e. g.,an electron beam.

,Vinyl monomers employed may be mono-functional, monoacrylates formed bythe esterification of acrylic or methacrylic acid and a C C preferably CC monohydric alcohol, e. g., methyl methacrylate, ethyl acrylate, butylacrylate, 2ethylhexyl acrylate, etc. The monomer mixture may alsoinclude a minor amount, e.g., about 1 to about 30 mole percent, ofdiacrylates, e.g., the diester of acrylic or methacrylic acid and a C Cdiol such as ethylene glycol diacrylate, 1,3 butylene diacrylate, 1,3butylene dimethacrylate, 1,6 hexamethylene diacrylate, 1,6 hexamethylenedimethacrylate, etc.

Monovinyl. hydrocarbons, e.g., styrene, alpha methyl styrene, vinyltoluene, etc., may also be used either alone or in combination with theaforementioned monoacrylates. Minor amounts, e.g., about 1 to about 30mole percent of the vinyl monomer mixture may be made up of divinylhydrocarbons such as divinyl benzene. Other vinyl monomers, e.g.,acrylonitrile, methacrylonitrile, vinyl acetate, etc., may be employedin minor amounts, e.g., about 1 to about 30 mole percent.

Advantageously, at least 70 weight percent of the vinyl monomercomponent is made up of monoacrylates selected from esters of a C Cmonohydric alcohol and acrylic or methacrylic acid and/or inoriovinylhydrocarbons having about eight to about nine carbon atoms. Frequently,it is advantageous to use a mixture of about 40 to about 60 mole percentof these monoacrylates and about 60 to about 40 mole percent of themonovinyl hydrocarbons.

V. PREPARATION AND APPLICATION OF THE COATING SOLUTION TO A SUBSTRATE Byadjusting the viscosity of the coating solution to a viscositycompatible with the desired method of coating, these coatings may beapplied by any of the conventional methods, e.g., brushing, spraying,roll coating, curtaincoating, flow coating, etc.

The viscosity of the paint binder solution may be adjusted by varyingthe molecular weight of the rubber-urethane-acrylate addition product.This may be accomplished by controlling the average number offunctionalgroups per molecule through control of the concentration ofthe hydroxy-alkyl acrylate constituent in forming the rubber particle.The viscosity may also be regulated by varying the relativeconcentration of the resin component with respect to the vinylmonomercomponent and/or by varying the relative concentration ofdissimilar monomers within the vinyl monomer component. The bindersolution may be applied to the substrate essentially free ofnon-polymerizable, organic solvents and/or diluents or it may be appliedwith the solvents and/or diluents in a method of application wherein thesolvent and/or diluents are flashed ofi' prior to polymerization.

The coatingsmay be applied to any substrate, e.g., metal, wood, glass,shaped polymeric solids, etc. These coatings will ordinarily be appliedtoan average depth in the range of about 0.1 to about 4 mils, morecommonly about 0.5 to about 2 mils.

VI. CURING OF THE COATING The films formed of the paints of thisinvention can be cured with ionizing radiation at relatively lowtemperatures, e.g., room temperature (20 to 25 C.) or a temperaturebetween room temperature and that temperature at which significantvaporization of its most volatile component is initiated, ordinarilybetween 20 C. and 75 C. The radiation is applied at dose rates of about0.1 to about Mrad per second on a workpiece, preferably a movingworkpiece, with the coating receiving a total dose in the rangeof about1 to about 25, more commonly about 8 to about 15 Mrad.

The term ionizing radiation as employed herein means radiation havingsufi'lcient energy to remove an electron from a gas atom, forming anion, hence radiation with minimum energy of, or equivalent to, about5,000 electron volts except when the curing is carried out in a vacuum.The preferred method of curing films of the instant paint binders uponthe substrates to which they have been applied is by subjecting suchfilms to a beam of polymerization efiecting electrons which at itssource of emission is within the range of, or equivalent to, about100,000 to about 500,000 electron volts. If irradiation is carried outinvacuum or at reduced pressure, this energy may be considerably lower.In this method of curing, it is preferred to employ a minimum of about25,000 electron volts per inch of distance between the radiation emitterand the workpiece where the intervening space is occupied by air orother gas of comparable density. Adjustment is made for the relativeresistance of the intervening gas which is preferably an oxygen-free,inert gas such as nitrogen or heli- In this application, the term paintis meant to include finely ground pigment and/or filler in the binder,the binder without pigment and/or filler or having very little of thesame, which can be tinted, if desired. Thus, the binder which isultimately converted to a durable film resistant to wear, weather, etc.,can be all or virtually all that is used to form the film, or it can bea vehicle for pigmentary and/or mineral filler material.

The abbreviation Mrad as employed herein means 1 million rad. The termrad as employed herein means that dose of radiation which results in theabsorption of 100 ergs of energy per gram of absorber, i.e., coatingfilm. The electron emitting means may be a linear electron acceleratorcapable of producing a direct current potential in the rangehereinbefore mentioned. In such device, electrons are ordinarily emittedfrom a hot filament and accelerated through a uniform voltage gradient.The electron beam, which may be about A; inch in diameter at this point,is then scanned in one direction to make a fan-shaped beam and thenpassing through a metal window, e.g., aluminum, aluminum-copper alloy,or magnesium-thorium alloy of about 0.003 inch thickness.

This invention will be more fully understood from the followingexamples:

EXAMPLE 1 v l. Rubber particles are prepared in aqueous medium usingabout 1/9 of a monomer mixture consisting of 521 parts by weight butylacrylate and 48.5 parts by weight 1,3 butylene dimethacrylate. Thismixture is stirred to establish dispersion of the monomers and 3.14parts by weight potassium persulfate dissolved in 71.4 parts by weightwater are added to the stirred mixture. This mixture is heated to 45 C.After about minutes, addition of the remainder of this monomer mixtureis begun at a rate such that the temperature of the reaction mixture ismaintained at 47 to 50 C. During the addition of the last two thirds ofthe monomer mixture, 5.72 parts by weight sodium dodecyl sulfatedissolved in 35.7 parts by weight water are added at a substantiallyconstant rate. During the addition of the last one-third of the monomermixture there are added 65 parts by weight hydroxyethyl acrylate. Thereaction mixture is maintained at 47 to 50 C. for about 2 hours.

The emulsion is then coagulated by addition of about grams ofconcentrated hydrochloric acid solution and 100 ml of water. The rubberparticles are isolated by filtration and washed with methanol containing1 weight percent of hydrochloric acid. The particles are thendried.

11. Determination of the concentration of reactive hydroxyl groups onthe surfaces of the particles is made by the well known method ofanalysis wherein the hydroxyl groups are reacted with acetic anhydrideusing a pyridine catalyst. The acetic acid is back titrated with sodiumhydroxide. For details, reference is made to C. A. Steyermark,Quantitative Organic Analysis, pp. 302-303 published by BlakistonCompany, New York, Toronto, and Philadelphia( 1951).

Ill. The hydroxy-functional rubber particles prepared in I above arereacted with a diisocyanate using the following procedures: Thehydroxy-functional particles in the quantity providing 1 mole ofreactive hydroxyl groups on the collective surfaces thereof aresuspended in toluene and 2,4 toluene diisocyanate, in the quantitynecessary to provide about 3 isocyanate groups per each hydroxyl group,is incrementally added at a rate slow enough to keep the temperature ofthe reaction mix below 32 C. fter the initial exotherm subsides, thereaction mixture is stirred for 1 hour.

IV. The rubber-diisocyanate adduct is mixed with a hydroxyalkyl acrylateusing the following procedure: The temperature of the reaction mix israised to about 45 C. and hydroxyethyl methacrylate monomer is added inslight excess (e.g., 5 to 7 percent excess) of that required to reactwith the unreacted isocyanate groups. It is added slowly andincrementally and the reaction is stirred continuously for severalhours. The solvent is removed under vacuum until the solvent content ofthe product mix is less than 15 percent. The rubberurethane-acrylateaddition product, hereinafter referred to as resin, is ready foremployment in coating compositions.

V. Paint dispersions are prepared form the rubber-urethane acrylateresin and vinyl monomers: The rubber-urethane-acrylate resin is dividedinto three fractions and each is diluted with methyl methacrylatemonomer to form three paint dispersions. The first paint dispersioncontains about 75 weight percent rubber-urethane-acrylate resin andabout weight percent methyl methacrylate. The second paint dispersioncontains about 50 weight percent of the rubbenurethaneacrylate and about50 weight percent methyl methacrylate. The third paint dispersioncontains about 25 weight percent of the rubber-urethane-acrylate resinand about 75 weight percent methyl methacrylate.

Vl. Coating of substrates: The dispersions prepared in V. above areseparately coated on substrates of steel, wood, glass and polymericsolids, i.e., acrylonitrile-butadiene-styrene copolymer, to an averagedepth of about 7/10 mil (0.0007

inch) and irradiated with an electron beam. The conditions ofirradiation are as follows:

Potential 275 KV Current milliamperes Distance, emitter from workpiece10 inches Dose l0 Mrad Atmosphere nitrogen' EXAMPLE 2 The procedure ofExample 1 is repeated with the difference that an equimolar amount ofethyl acrylate is substituted for the butyl acrylate used in the monomermixture to form the rubber particles and one half of the methylmethacrylate used to form the coating dispersions with therubber-urethane-acrylate addition product is replaced with an equimolaramount of styrene.

EXAMPLE 3 The procedure of Example 1 is repeated with the differencesthat an equimolar amount of 2-ethyl hexyl acrylate is substituted forthe butyl acrylate used in the monomer mixture to form the rubberparticle, and the vinyl monomer component used to form the coatingsolution with the rubberurethane-acrylate addition product (resin) is amixture of 30 mole percent methyl methacrylate, 20 mole percent butylmethacrylate, 10 mole percent 2-ethyl hexyl acrylate, 20 mole percentstyrene and 20 mole percent vinyl toluene.

EXAMPLE 4 The procedure of Example 1 is repeated with the differencesthat an equimolar amount of cyclohexyl acrylate is substituted for thebutyl acrylate and equimolar amounts of 1,3 butylene diacrylate issubstituted for the 1,3 butylene dimethacrylate used to form the rubberparticles and the vinyl monomer component used to form the coatingdispersion with the rubber-urethane-acrylate addition product is amixture of 70 mole percent methyl methacrylate, 20 mole percent alphamethyl styrene and 10 mole percent 1,3 butylene dimethacrylate.

EXAMPLE 5 The procedure of Example 1 is repeated with the differencethat an equimolar amount of 1,6 hexamethylene diacrylate is substitutedfor the 1,3 butylene dimethacrylate used to form the rubber particle.

EXAMPLE 6 The procedure of Example 1 was repeated with the differencesthat an equimolar amount of divinyl benzene is substituted for the 1,3butylene dimethacrylate used in the monomer mixture to form the rubberparticle and the vinyl monomer component used to form the coatingdispersion with the rubber-urethane-acrylate addition product is amixture of 60 mole percent methyl methacrylate, 20 mole percent styrene,10 mole percent butyl acrylate, and 10 mole percent divinyl benzene.

EXAMPLE 7 The procedure of Example 1 is repeated with the differencethat a single paint dispersion is formed using 60 weight percent of therubber-urethane-acrylate addition product and 40 weight percent of themethyl methacrylate.

EXAMPLE 8 The procedure of Example 1 is repeated with the differencethat a single paint dispersion is formed using 40 weight percent of arubber-urethane-acrylate addition product and 60 weight percent of themethyl methacrylate.

EXAMPLE 9 The procedure of Example 1 is repeated except for thedifferences that the monoacrylate component of the monomer mixture usedto form the rubber particle consists of about 5 mole percenthydroxyethyl methacrylate and about mole percent butyl acrylate. Themonomers are divided into five equal fractions for addition to thereaction mixture and the hydroxyethyl methacrylate is added in the fifthor last increment.

EXAMPLE 10 The procedure of Example 1 isrepeated except for thedifferences that the monoacrylate component of the monomer mixture usedto form the rubber particle consists of about 15 mole percenthydroxyethyl acrylate and about 85 mole percent butyl acrylate and thediacrylate is 1,3 butylene diacrylate. The monomer mixture is dividedinto about five equal fractions and the hydroxyethyl acrylate is addedin the fifth and last fraction.

EXAMPLE 11 The procedure of Example 1 is repeated with the differencesthat thecuring is carried out in a helium atmosphere and the potentialof the electron beam upon exit from the electron window into suchatmosphere is about 295 KV.

EXAMPLE 12 The procedure of Example 1 is repeated with the dil ferencesthat the curing is carried out in a nitrogen atmosphere containing aminor amount of CO and the potential of the electron beam upon exit fromthe electron window into such atmosphere is about 260 KV.

EXAMPLE 13 Materials Grams Ethyl acrylate 60.0 Hydroxyethyl methacrylate20.0 1,3-butylene dimethacrylate 20.0 Dispersion agent 3.0 AIBN 0.5

l An amphiphatic copolymer 1 portion soluble in the acrylic monomers andthe other portion soluble in the solvent, e.g., dodecane) is prepared byreacting l2 hydroxystearic acid (300 g.') in the presence of stearylalcohol (310 g.) and ptoluene sulfonic acid g.) at 180". 190C. until theacid value is less than 1 mg KOH/g. The'produclis then reacted withmethacrylic anhydride (170 g.) The resulting material is thencopolymerized with an equimolar amount of methyl methacrylale using AlBNinitiator (9 g.) and butyl acetate solvent. This method of producingthis dispersing agent is described in detail by K. E. J; Barratt and H.R. Thomas in Journal of Polymer Science, Part Al, Vol. 7, 2625' (1969).Other dispersing agents which are effective for stabilizing suspensionsin hydrocarbon liquids may be used in place ofthe above describedmaterials.

(2) 2,2 azobis (Lmethylpropionitrile).

B. Two-thirds of the mixture of the above listed materials, exceptingthe hydroxyethyl methacrylate, are added to 1,000 grams n-dodecane undernitrogen. the reaction mixture is warmed to 40 C. When the exothermstarts, the temperature is allowed to rise to 80 C. The temperature ismaintained at 80 C. for about minutes. The hydroxyethyl methacrylate andthe final one-third of the other materials are added slowly. Thetemperature is maintained at 80 C. for 30 minutes.

II. The hydroxy-functional rubber particles prepared in i above arereacted with a diisocyanate using the 1 following procedure: Thetemperature of the reaction mixture is allowed to cool to 30 C. andthereis slowly added 132 grams of 2,4 toluene diisocyanate. The temperatureis maintained in the range of 30" 35 C. for 2 hours.

Ill. There is added to the reaction mix 125 grams of hydroxyethylmethacrylate. The reaction mix is then heated at 45 C.

for 4 hours. The rubber-urethane-acrylate addition product particles areseparated from the solvent by filtration.

IV. A paint dispersion is prepared using 40 parts by weight of therubber-urethane-acrylate addition product and 60 parts by weight of anequimolar amount of methyl methacrylate and styrene.

I V. Coating of substrates: Paint dispersion prepared in IV is sprayedupon substrates of steel, aluminum, glass, paper, wood and polymericsolid, i.e., polypropylene. During the reaction step about l.5 mils andcured thereon placing said substrates in a nitrogen atmosphere andexposing the coated surfaces of the substrates to an electron beam(potential 275 KV current 30 miliamperes) until the coatings arecrosslinked upon the surfaces of the substrates and are tack-free to thetouch.

EXAMPLE 1 4 The procedure of Example 13 is repeated with the differencesthat an equimolar amount of 4,4 diphenylmethane diisocyanate with lisocyanate group per molecule blocked with caprolactam is substitutedfor the 2,4 toluene diisocyanate. In the reaction of the diisocyanatewith hydroxy functional rubber in Section II of the procedure of Example13 and the procedure of Section III of Example I3 is modified in that,as the hydroxyethyl methacrylate monomer is dispersed in the reactionmixture, the temperature of the reaction mixture is raised to about 150C. and maintained at a temperature of about 150 C. while the reactionmixture is stirred for about '30 minutes.

EXAMPLE 15 The procedure of Example 13 is repeated with the differencesthat an equimolar amount of l-phenoxy 2,4 phenylene diisocyanate with lisocyanate group per molecule blocked with caprolactam is substitutedfor the 2,4 toluene diisocyanate in the reaction of diisocyanate withhydroxyfunctional rubber in Section II of the procedure of Example 13and the procedure of Section III of Example 13 as modified in that, asthe hydroxyethyl methacrylate monomer is dispersed in the reactionmixture, the temperature is raised to about I 150 C. and maintained at atemperature of about 150 C.

while the reaction mixture is stirred for about 30 minutes.

EXAMPLE 16 The procedure of Example 13 is repeated with the differencesthat an equimolar amount of l-tert-butyl- 2,4 phenylene diisocyanatewith l isocyanate group per molecule blocked with caprolactam issubstituted for the 2,4 toluene diisocyanate in the reaction ofdiisocyanate with hydroxyfunctional rubber in Section II of theprocedure of Example 13 and the procedure of Section III of Example 13is modified in that, as the hydroxyethyl methacrylate monomer isdispersed in the reaction mixture, the temperature of the reactionmixture is raised to about C. and maintained at a temperature of about150 C. while the reaction mixture is stirred for about 30 minutes.

EXAMPLE 17 The procedure of Example 13 is repeated with the differencesthat an equimolar amount of lethyl- 2,4 phenylene diisocyanate with lisocyanate group per molecule blocked with caprolactam is substitutedfor the 2,4 toluene diisocyanate in the reaction of diisocyanate withhydrox'y-functional rubber in Section II of the procedure of Example 13and the procedure of Section III of Example 13 is modified in that, asthe hydroxyethyl methacrylate monomer is dispersed in the reactionmixture, the temperature of the reaction mixture is raised to about 150C. and maintained at a temperature of about 150 C. while the reactionmixture is stirred for about 30 minutes.

EXAMPLE 18 The procedures of Examples 1 and 13 are repeated except forthe difference that a functionally equivalent amount of1,1,l-trimethylolethane triacrylate is substituted for the 1,3- butylenedimethacrylate inthe formation of the hydroxy-functional rubberparticle.

EXAMPLE 19 The procedures of Examples 1 and 13 are repeated except forthe difference that a functionally equivalent amount ofl,l,l-trimethylolpropane, trimethacrylate is substituted for the1,3-butylene dimethacrylate in the formation of the hydroxy-functionalrubber particle.

EXAMPLE 20 The procedures of Examples 1 and 13 are repeated except forthe difference that a functionally equivalent amount of1,4-dimethylolcyclohexane dimethacrylate is substituted for the1,3-butylene dimethacrylate in the formation of the hydroxy-functionalrubber particles.

The terms acrylate and acrylates, when used herein without a modifierdistinguishing between esters of acrylic and methacrylic acid, shall beunderstood to include both. This, of course, does not apply to thenaming of a specific compound.

it will be understood by those skilled in the art that modifications canbe made within the foregoing examples within the scope of the inventionas hereinbefore described and hereinafter claimed.

We claim:

1. A rubber-urethane-acrylate addition product formed by reacting afirst isocyanate group of a diisocyanate with a hydroxy-functionalelastomeric particle of crosslinked acrylic polymer and reacting theremaining isocyanate group of said diisocyanate with a hydroxyalkylacrylate, said particle of crosslinked acrylic polymer consistingessentially of 1. about 80 to about 98 mole percent of a monoacrylatecomponent which consists essentially of about 70 to about 95 molepercent of a monoester of acrylic acid and a C C monohydric alcohol andabout 5 to about 30 mole percent of a hydroxy-functional acrylateselected from hydroxyethyl acrylate, hydroxyethyl methacrylate,hydroxypropyl acrylate and hydroxypropyl methacrylate, and

2. about 2 to about 20 mole percent of divinyl benzene, a diester ofacrylic or methacrylic acid and a C C dihydric alcohol or a triester ofacrylic acid or methacrylic acid and a C C trihydric alcohol.

2. A rubber-urethane-acrylate addition product in accordance with claiml wherein said particle of crosslinked acrylic rubber has averagediameter in the range of about 0.04 to 1 micron.

3. A rubber-urethane-acrylate addition product in accordance with claim1 wherein said monoester of acrylic acid is butyl acrylate and saiddiacrylate isselected from 1,3 butylene diacrylate and 1,3 butylenedimethacrylate.

4. A rubber-urethane-acrylate addition product in accordance with claim1 wherein said monoester of acrylic acid is butyl acrylate and saiddiacrylate is selected from 1,3 butylene diacrylate and 1,3 butylenedimethacrylate.

5. A rubber-urethane-acrylate addition product in accordance with claim1 wherein said diisocyanate is toluene diisocyanate.

6. A rubber-urethane-acrylate addition product in accordance with claim1 wherein said hydroxyalkyl acrylate is selected from hydroxyethylacrylate, hydroxyethyl methacrylate hydroxypropyl acrylate andhydroxypropyl methacrylate.

7. A rubber-urethane-acrylate addition product formed by reacting afirst isocyanate group of a diisocyanate with a hydroxy-functionalelastomeric particle of crosslinked acrylic polymer and reacting theremaining isocyanate group of said diisocyanate with a hydroxyalkylacrylate, said particle of crosslinked acrylic polymer consisting of 1.about 80 to about 98 mole percent of a monoacrylate component whichconsists essentially of about 65 to about 98 mole percent of a monoesterof acrylic acid and a C C monohydric alcohol and about 2 to about 35mole percent of a hydroxy-functional acrylate selected from hydroxyethylacrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate andhydroxypropyl methacrylate, and

2. about 2 to about 20 mole percent of divinyl benzene, a diester ofacrylic or methacrylic acid and a C C dihydric alcohol or a triester ofacrylic or methacrylic acid and a C C trihydric alcohol.

8. A radiation-curable paint which on a pigment and mineral filler-freebasis comprises a film-forming dispersion of about 35 to about 65 weightpercent vinyl monomers and about 70 to about 35 weight percent of arubber-urethaneacrylate addition product formed by reacting a firstisocyanate group of a diisocyanate with a hydroxy-functional elastomericparticle of crosslinked acrylic polymer and reacting the remainingisocyanate group of said diisocyanate with a hydroxyalkyl acrylate, saidparticle of crosslinked acrylic polymer consisting essentially of 1.about to about 98 mole percent of a monoacrylate component whichconsists essentially of about 70 to about 95 mole percent of a monoesterof acrylic acid and a C C monohydric alcohol and about 5 to about 30mole percent of a hydroxy-functional acrylate selected from hydroxyethylacrylate hydroxyethyl methacrylate, hydroxypropyl acrylate andhydroxypropyl methacrylate, and

2. about 2 to about 20 mole percent of divinyl benzene, a diester ofacrylic or methacrylic acid and a C C dihydric alcohol or a triester ofacrylic acid or methacrylic acid and a C C trihydric alcohol. I

9. A radiation-curable paint which on a pigment and mineral filler-freebasis comprises a film-forming dispersion of about 20 to about weightpercent vinyl monomers and about 80 to about 10 weight percent of arubber-urethaneacrylate'addition product formed by reacting a firstisocyanate group of a diisocyanate with a hydroxy-functional elastomericparticle of crosslinked acrylic polymer and reacting the remainingisocyanate group of said diisocyanate with a hydroxyalkyl acrylate, saidparticle of crosslinked acrylic polymer consisting essentially of 1.about 80 to about 98 mole percent of a monoacrylate component whichconsists essentially of about 65 to about 98 mole percent of a monoesterof acrylic acid and a C C monohydric alcohol and about 2 to about 35mole percent of a hydroxy-functional acrylate selected from hydroxyethylacrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate andhydroxypropyl methacrylate, and

2. about 2 to about 20 mole percent of divinyl benzene, a diester ofacrylic or methacrylic acid and a C C dihydric alcohol or a triester ofacrylic or methacrylic acid and a C C trihydric alcohol.

10. The method of coating a substrate which comprises A. applying to asurface of said substrate a film of radiationcurable paint which on apigment and mineral filler-free basis comprises a film-formingdispersion of about 20 to about 90 weight percent vinyl monomers andabout 80 to about 10 weight percent of a rubber-urethane-acrylateaddition product formed by reacting a first isocyanate group of adiisocyanate with a hydroxyalkyl acrylate, said particle of crosslinkedacrylic polymer consisting essentially of about 80 to about 98 molepercent of a monoacrylate component which consists essentially of about65 to about 98 mole percent of a monoester of acrylic acid and a C Cmonohydric alcohol and about 2 to about 35 mole percent of ahydroxy-functional acrylate selected from hydroxyethyl acrylate,hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropylmethacrylate, and

2. about 2 to about20 mole percent of divinyl benzene, a

diester of acrylic or methacrylic acid and a C C dihydric alcohol ortriester of acrylic or methacrylic acid and a C C dihydric alcohol or atriester of acrylic or methacrylic acid and a C C trihydric alcohol, and

B. crosslinkingsaid film upon said substrate by exposing said substrateto a beam of electrons having average energy in the range of about100,000 to about 500,000 electron volts. 7 11. An article of manufacturecomprising in combination a substrate and a coating thereon comprisingthe polymerization product of a film-forming dispersion crosslinked insitu by ionizing radiation, said film-forming dispersion on a pigmentand particulate filler-free basis consisting essentially of arubber-urethane-acrylate addition product formed by reacting a firstisocyanate group of a diisocyanate with a hydroxy-functi onalelastomeric particle of crosslinked acrylic polymer and reacting theremaining isocyanate group of said diisocyanate with a hydroxyalkylacrylate, said particle of crosslinked acryl- 1 ic polymer consistingessentially of 1. about 80 to about 98 mole percent of a monoacrylatecomponent which consists essentially of about 70 to about 95 molepercentof a monoester of acrylic acidand a C C monohydric alcohol and about 5to about 30 mole percent of a hydroxy-functional acrylate selected fromhydroxyethyl acrylate, hydroxyethyl methacrylate,

hydroxypropyl acrylate and hydroxypropyl methacrylate,

an 2. about 2 to about 20 mole percent of divinyl benzene, a diester ofacrylic or methacrylic acid and a C C dihydric alcohol or a triester ofacrylic acid or methacrylic acid and a C C trihydric alcohol. 12. Anarticle of manufacture comprising in combination a substrate and acoating thereon comprising the polymerization product of a film-formingdispersion crosslinked in situ by ionizing radiation, said film-formingdispersion on a pigment and particulate filler-free basis consistingessentially of about 20 to about 90 weight percent vinyl monomers andabout 80 to about 10 weight percent of a rubber-urethane-acrylateaddition product formed by reacting a first isocyanate group of adiisocyanate with a hydroxy-functional elastomeric particle ofcross-linked acrylic polymer and reacting the remaining isocyanate groupof said diisocyanate with a hydroxyalkyl acrylate, said particle ofcrosslinked acrylic polymer consisting essentially of about 20 to about90 weight percent vinyl monomers and about 80 to about 10 weight percentof a rubber-urethane-acrylate addition product formed by reacting afirst isocyanate group of a diisocyanate with a hydroxy-functionalelastomeric particle of crosslinked acrylic polymer and reacting theremaining isocyanate group of said diisocyanate with a hydroxyalkylacrylate, said particle of crosslinked acrylic polymer consistingessentially of 1. about 80 to about 98 mole percent of a monoacrylatecomponent which consists essentially of about 65 to about 98 molepercent of a monoester of acrylic acid and a C C monohydric alcohol andabout 2 to about mole percent of a hydroxy-functional acrylate selectedfrom hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropylacrylate and hydroxypropyl methacrylate, and 2. about 2 to about 20 molepercent of divinyl benzene, a diester of acrylic or methacrylic acid anda C C dihydric alcohol or a triester of acrylic or methacrylic acid anda C C trihydric alcohol.

2. about 2 to about 20 mole percent of divinyl benzene, a diester ofacrylic or methacrylic acid and a C2 - C8 dihydric alcohol or a triesterof acrylic or methacrylic acid and a C2 -C8 trihydric alcohol.
 2. about2 to about 20 mole percent of divinyl benzene, a diester of acrylic ormethacrylic acid and a C2 - C6 dihydric alcohol or a triester of acrylicacid or methacrylic acid and a C2 - C6 trihydric alcohol.
 2. Arubber-urethane-acrylate addition product in accordance with claim 1wherein said particle of crosslinked acrylic rubber has average diameterin the range of about 0.04 to 1 micron.
 2. about 2 to about 20 molepercent of divinyl benzene, a diester of acrylic or methacrylic acid anda C2 - C6 dihydric alcohol or a triester of acrylic acid or methacrylicacid and a C2 - C6 trihydric alcohol.
 2. About 2 to about 20 molepercent of divinyl benzene, a diester of acrylic or methacrylic acid anda C2 - C8 dihydric alcohol or a triester of acrylic or methacrylic acidand a C2 -C8 trihydric alcohol.
 2. about 2 to about 20 mole percent ofdivinyl benzene, a diester of acrylic or methacrylic acid and a C2 - C8dihydric alcohol or triester of acrylic or methacrylic acid and a C2 -C8dihydric alcohol or a triester of acrylic or methacrylic acid and a C2 -C8 trihydric alcohol, and B. crosslinking said film upon said substrateby exposing said substrate to a beam of electrons having average energyin the range of about 100,000 to about 500,000 electron volts.
 2. about2 to about 20 mole percent of divinyl benzene, a diester of acrylic ormethacrylic acid and a C2 - C6 dihydric alcohol or a triester of acrylicacid or methacrylic acid and a C2 - C6 trihydric alcohol.
 2. about 2 toabout 20 mole percent of divinyl benzene, a diester of acrylic ormethacrylic acid and a C2 - C8 dihydric alcohol or a triester of acrylicor methacrylic acid and a C2 -C8 trihydric alcohol.
 3. Arubber-urethane-acrylate addition product in accordance with claim 1wherein said monoester of acrylic acid is butyl acrylate and saiddiacrylate is selected from 1,3 - butylene diacrylate and 1,3 - butylenedimethacrylate.
 4. A rubber-urethane-acrylate addition product inaccordance with claim 1 wherein said monoester of acrylic acid is butylacrylate and said diacrylate is selected from 1,3 - butylene diacrylateand 1,3 - butylene dimethacrylate.
 5. A rubber-urethane-acrylateaddition product in accordance with claim 1 wherein said diisocyanate istoluene diisocyanate.
 6. A rubber-urethane-acrylate addition product inaccordance with claim 1 wherein said hydroxyalkyl acrylate is selectedfrom hydroxyethyl acrylate, hydroxyethyl methacrylate hydroxypropylacrylate and hydroxypropyl methacrylate.
 7. A rubber-urethane-acrylateaddition product formed by reacting a first isocyanate group of adiisocyanate with a hydroxy-functional elastomeric particle ofcrosslinked acrylic polymer and reacting the remaining isocyanate groupof said diisocyanate with a hydroxyalkyl acrylate, said particle ofcrosslinked acrylic polymer consisting of
 8. A radiation-curable paintwhich on a pigment and mineral filler-free basis comprises afilm-forming dispersion of about 35 to about 65 weight percent vinylmonomers and about 70 to about 35 weight percent of arubber-urethane-acrylate addition product formed by reacting a firstisocyanate group of a diisocyanate with a hydroxy-functional elastomericparticle of crosslinked acrylic polymer and reacting the remainingisocyanate group of said diisocyanate with a hydroxyalkyl acrylate, saidparticle of crosslinked acrylic polymer consisting essentially of
 9. Aradiation-curable paint which on a pigment and mineral filler-free basiscomprises a film-forming dispersion of about 20 to about 90 weightpercent vinyl monomers and about 80 to about 10 weight percent of arubber-urethane-acrylate addition product formed by reacting a firstisocyanate group of a diisocyanate with a hydroxy-functional elastomericparticle of crosslinked acrylic polymer and reacting the remainingisocyanate group of said diisocyanate with a hydroxyalkyl acrylate, saidparticle of crosslinked acrylic polymer consisting essentially of 10.The method of coating a substrate which comprises A. applying to asurface of said substrate a film of radiation-curable paint which on apigment and mineral filler-free basis comprises a film-formingdispersion of about 20 to about 90 weight percent vinyl monomers andabout 80 to about 10 weight percent of a rubber-urethane-acrylateaddition product formed by reacting a first isocyanate group of adiisocyanate with a hydroxyalkyl acrylate, said particle of crosslinkedacrylic polymer consisting essentially of
 11. An article of manufacturecomprising in combination a substrate and a coating thereon comprisingthe polymerization product of a film-forming dispersion crosslinked insitu by ionizing radiation, said film-forming dispersion on a pigmentand particulate filler-free basis consisting essentially of arubber-urethane-acrylate addition product formed by reacting a firstisocyanate group of a diisocyanate with a hydroxy-functional elastomericparticle of crosslinked acrylic polymer and reacting the remainingisocyanate group of said diisocyanate with a hydroxyalkyl acrylate, saidparticle of crosslinked acrylic polymer consisting essentially of
 12. Anarticle of manufacture comprising in combination a substrate and acoating thereon comprising the polymerization product of a film-formingdispersion crosslinked in situ by ionizing radiation, said film-formingdispersion on a pigment and particulate filler-free basis consistingessentially of about 20 to about 90 weight percent vinyl monomers andabout 80 to about 10 weight percent of a rubber-urethane-acrylateaddition product formed by reacting a first isocyanate group of adiisocyanate with a hydroxy-functional elastomeric particle ofcross-linked acrylic polymer and reacting the remaining isocyanate groupof said diisocyanate with a hydroxyalkyl acrylate, said particle ofcrosslinked acrylic polymer consisting essentially of about 20 to about90 weight percent vinyl Monomers and about 80 to about 10 weight percentof a rubber-urethane-acrylate addition product formed by reacting afirst isocyanate group of a diisocyanate with a hydroxy-functionalelastomeric particle of crosslinked acrylic polymer and reacting theremaining isocyanate group of said diisocyanate with a hydroxyalkylacrylate, said particle of crosslinked acrylic polymer consistingessentially of